Weld Detail Fatigue Life Improvement Techniques

1 NTIS # PB97-193031 SSC-400 weld Detail Fatigue LIFE Improvement Techniques This document has been approved For public release and sale; its Distribution is unlimited SHIP STRUCTURE COMMITTEE 1997 SHIP STRUCTURE COMMITTEE RADM Robert C. North U. S. Coast Guard Assistant Commandant, Marine Safety and Environmental Protection Chairman, Ship Structure Committee Mr. Robert McCarthy Director, Survivability and Structural Integrity Group Naval Sea Systems Command Dr. Donald Liu Senior Vice President American Bureau of Shipping Mr.

2 Edwin B. Schimler Director, Office of Ship Construction Maritime Administration Mr. John Grinstead Director General, Marine Safety, Safety & Security Transport Canada Mr. Thomas Connors Director of Engineering Military Sealift Command Dr. Neil Pegg Group Leader - Structural Mechanics Defence Research Development Canada CONTRACTING OFFICER TECHNICAL REP. Mr. William J. Siekierka Naval Sea Systems Command EXECUTIVE DIRECTOR Lieutenant Tom Miller U. S. Coast Guard SHIP STRUCTURE SUB-COMMITTEE AMERICAN BUREAU OF SHIPPING DEFENCE RESEARCH ESTABLISHMENT ATLANTIC Mr.

3 Glenn Ashe Mr. John F. Conlon Mr. Phil Rynn Mr. William Hanzalek Mr. Layton Gilroy LCDR Stephen Gibson Dr Roger Hollingshead Mr. John Porter MARITIME ADMINISTRATION MILITARY SEALIFT COMMAND Mr. Chao Lin Mr. Richard P. Voelker Mr. Paul Gilmour Dr. Walter M. Maclean Mr. Robert E. VanJones Mr. Rick A. Anderson Mr. Jeffery E. Beach Mr. Michael W. Touma NAVAL SEA SYSTEMS COMMAND TRANSPORT CANADA Mr. W. Thomas Packard Mr. Edward E. Kadala Mr. Allen H. Engle Mr. Charles L. Null Mr. Peter Timonin Mr. Felix Connolly Mr.

4 Francois Lamanque UNITED STATES COAST GUARD CANADIAN COAST GUARD Captain Mark VanHaverbeke Mr. Rubin Sheinberg Mr. Walt Lincoln Mr. Daniel Gauvin Member Agencies: American Bureau of Shipping Defence Research Establishment Atlantic Maritime Administration Military Sealift Command Naval Sea Systems Command Transport Canada United States Coast Guard An Interagency Advisory Committee Address Correspondence to: Executive Director Ship Structure Committee Coast Guard (G-MSE/SSC) 2100 Second Street, Washington, 20593-0001 Ph: (202) 267-0143 Fax.

5 (202) 267-4816 SSC - 400 SR - 1379 August 26, 1997 weld Detail Fatigue LIFE Improvement Techniques Fatigue cracks in steel ships often occur at welded joints where stress concentrations due to the joint geometry are relatively high and the Fatigue strength of the weld is reduced in comparison to that of the base metal. This becomes more critical in ships built of High Strength Steels (HSS) because the Fatigue strength of steel in the as-welded condition does not increase in proportion to the yield or tensile strength.

6 In many cases, the Fatigue performance of severely loaded details can be improved by employing good Detail design practices, for example by upgrading the welded Detail class to one having a higher Fatigue strength. In some cases, however, there may be no better alternatives to the Detail in question and modification of the Detail may not be practicable. As an alternative to strengthening the structure at a considerable increase in costs, procedures which reduce the severity of the stress concentration at the weld , remove imperfections, and / or introduce local compressive stresses at the weld can be used for Improvement of the Fatigue life.

7 Similarly, these Fatigue Improvement Techniques can be applied as remedial measures to extend the Fatigue life of critical welds that have failed prematurely and have been repaired. To date, weld Fatigue life Improvement Techniques have been successfully applied in several industries. While there has been increasing interest in the application of Fatigue life Improvement Techniques to ship structures, at present there is a lack of guidance on the use of such Techniques for design, construction and repair.

8 Hence the key elements of this project were to compile available data on Fatigue life Improvement Techniques , assess the feasibility and practicality for their application to ship details , identify gaps in the technology, and finally to recommend design, construction and repair requirements. ROBERT C. NORTH Rear Admiral, U. S. Coast Guard Chairman, Ship Structure Committee Ship Structure Committee Technical Report Documentation Page 1. Report No. SSC-400 2. Government Accession No.

9 PB97-193031 3. Recipient s Catalog No. 4. Title and Subtitle 5. Report Date December 1996 weld Detail Fatigue LIFE Improvement Techniques 6. Performing Organization Code 7. Author(s) Kirkhope, R. Bell, L. Caron and Basu 8. Performing Organization Report No. SR-1379 9. Performing Organization Name and Address MIL Systems Engineering 10. Work Unit No. (TRAIS) 200 1150 Morrison Drive Ottawa, Ontario, CANADA K2H 8S9 11. Contract or Grant No. 94-234-4E01031 12. Sponsoring Agency Name and Address Ship Structure Committee C/O Commandant (G-MSE/SSC) United States Coast Guard 13.

10 Type of Report and Period Covered Final Report 2100 Second Street, SW Washington, DC 20593-0001 14. Sponsoring Agency Code G-M 15. Supplementary Notes Sponsored by the Ship Structure Committee and its member agencies 16. Abstract Fatigue cracks in steel ships often occur at welded joints where stress concentrations due to the joint geometry are relatively high and the Fatigue strength of the weld is reduced in comparison to that of the base metal. This becomes more critical in ships built of High Strength Steels (HSS) because the Fatigue strength of steel in the as-welded condition does not increase in proportion to the yield or tensile strength.